The present invention relates to a plate-making method and a plate-making apparatus, which perform digital plate-making, and also relates to a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which perform the digital plate-making on a press and subsequently perform printing. More specifically, the present invention relates to a plate-making method, a plate-making apparatus, a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, where the ink transportation line in an ink jet method of ejecting an oil in using electrostatic field has a cleaning function and thereby, good image quality can be attained in the plate-making and in the printing.
In the lithographic printing, the printing is performed by forming a printing ink-receptive region and a printing ink-repulsive region on the surface of a printing plate in correspondence to an image original and adhering a printing ink to the ink-receptive region. Usually, hydrophilic and lipophilic (ink-receptive) regions are imagewise formed on the surface of a printing plate and the hydrophilic region is rendered ink-repulsive using a fountain solution.
In general, the recording of an image on a printing original plate (plate-making) is performed by a method of once outputting an image original on a silver salt photographic film in an analog or digital manner, exposing a diazo resin or photopolymerizable photopolymer light-sensitive material (printing original plate) through the film and then, dissolving and removing the non-image area using an alkaline developer.
In recent years, the lithographic printing process is demanded to meet requirements for more improvement in the digital drawing technique and higher efficiency in the process thereof and for satisfying these requirements, a large number of systems for directly drawing digital image information on a printing original plate have been proposed. These techniques are called CTP (computer-to-plate) or DDPP (digital direct printing plate). With respect to the plate-making method, for example, a system of recording an image in the light or heat mode using a laser has been proposed and this system is partially put into practical use.
However, in this plate-making method, irrespective of light mode or heat mode, the plate-making generally involves a treatment with an alkaline developer after the laser recording to dissolve and remove the non-image area and therefore, an alkaline waste solution is discharged. This is not preferred in view of the environmental conservation.
As means for realizing an efficient printing process, a system of performing the image drawing on a press is known. In the above-described method of using a laser, an expensive and large-scale apparatus is necessary. In this respect, a system applying an ink let method which is an inexpensive and compact recording device, has been proposed.
JP-A-4-97848 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a method of providing a plate drum having a hydrophilic or lipophilic surface part in place of the conventional plate cylinder, forming thereon a lipophilic or hydrophilic image by an ink jet method, removing and cleaning the image after the completion of printing. In this method, however, it is difficult to attain easy removing (namely, cleaning) of the printed image and a sufficiently long press life at the same time. In the case of forming an image having a high press life on a plate cylinder, an ink containing a resin in a relatively high concentration must be used and accompanying the evaporation of solvent at the nozzle part, the resin readily fixes to the ink jet means of forming a printing image, as a result, the ink ejection stability decreases and a good image cannot be obtained.
JP-A-64-27953 discloses a method of drawing an image on a hydrophilic plate material by an ink jet method using a lipophilic wax ink, thereby performing plate-making. In this method, the image is formed by a wax and therefore, the image area is weak in the mechanical strength and deficient in the adhesive property to the hydrophilic surface of the plate material, which gives rise to poor press life.
A plate-making method and a plate-making apparatus using an ink jet method of ejecting an oil ink using an electrostatic field are recently attracting attention. In this ink jet method, however, it has been found that the adhesion of dust and fixing of ink to the ejection electrode deteriorate the ejection performance and also, the ink fixing on the passage of the ink circulation line decreases the ink flow rate to cause deterioration in the ejection performance.
The problem to be solved in the present invention is to provide a method of removing attachments to the ejection electrode and on the passage of ink circulation line.
The present invention has been made by taking account of the above-described problems.
A first object of the present invention is to provide a plate-making method, a plate-making apparatus, a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which can adopt the digital technique not requiring a development processing.
A second object of the present invention is to provide a plate-making method, a plate-making apparatus, a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, where a lithographic printing plate capable of creating a large number of clear and high-quality printed matters can be manufactured inexpensively by a simple and easy method.
A third object of the present invention is to provide a plate-making method, a plate-making apparatus, a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, where attachments to the ejection electrode and on the passage of the ink circulation line can be removed.
Other objects and effects of the present invention will become apparent from the following description.
The above-described objects of the present invention have been achieved by providing the followings.
1) A plate-making method comprising:
forming an image directly on a plate material by an electrostatic ink jet method comprising ejecting an oil ink using electrostatic field based on signals of image data; and
fixing said image to manufacture a printing plate,
wherein said method uses:
(1) an ink circulation line having the following members a, b and c:
a. an ink jet ejection head,
b. an ink transportation line comprising an ink feed line for feeding said oil ink to said ink jet ejection head and an ink recovery line for recovering said oil ink from said ink jet ejection head, and
c. an ink tank for storing said oil ink;
(2) a cleaning solution feed line for feeding a cleaning solution to said ink transportation line; and
(3) a cleaning solution recovery line for recovering said cleaning solution from said ink transportation line, and
wherein at the time of cleaning, said ink tank is separated from said ink transportation line, said cleaning solution feed line and said cleaning solution recovery line are connected to said ink transportation line, and a cleaning solution is transported to the ink transportation line to perform the cleaning.
2) The plate-making process according to item 1) above, wherein said cleaning solution is circulated at the time of cleaning.
3) The plate-making method according to item 1) or 2) above, wherein the flow rate of said cleaning solution at the time of cleaning is higher than the flow rate of ink at the time of drawing an image.
4) The plate-making method according to any one of items 1 to 3 above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
5) A plate-making apparatus comprising:
an image-forming unit which forms an image directly on a plate material; and
an image-fixing unit which fixes the image formed by said image-forming unit to obtain a printing plate,
wherein said image-forming unit comprises:
an ink jet drawing device having an ink jet ejection head from which an oil ink is ejected using electrostatic field based on signals of image data,
an ink circulation unit comprising:
(1) said ink jet ejection head,
(2) an ink transportation unit comprising an ink feed member which feeds said oil ink to said ink jet ejection head and an ink recovery member which recovers said oil ink from said ink jet ejection head, and
(3) an ink tank for storing said oil ink,
a cleaning solution feed member which feeds a cleaning solution to said ink transportation unit,
a cleaning solution recovery member which recovers said cleaning solution from said ink transportation unit,
a feed side changeover member which separates said ink tank from said ink transportation unit and at the same time, connects said cleaning solution feed member to said ink transportation unit, and
a recovery side changeover member which connects said cleaning solution recovery member to said ink transportation unit.
6) The plate-making apparatus according to item 5) above, further comprising a circulation unit which circulates said cleaning solution at the time of cleaning.
7) The plate-making apparatus according to item 5) or 6) above, further comprising a flow rate-changing member capable of increasing the flow rate of said cleaning solution at the time of cleaning higher than the flow rate of ink at the time of drawing an image.
8) The plate-making apparatus according to any one of items 5) to 7) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9m or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
9) The plate-making apparatus according to any one of items 5) to 8) above, wherein said image-fixing unit has a heating member comprising at least one of a heat roller and a lamp selected from an infrared lamp, a halogen lamp and a xenon flash lamp.
10) The plate-making apparatus according to item 9) above, wherein said heating member is disposed or controlled to gradually elevate the temperature of said plate material at the time of fixing said image.
11) The plate-making apparatus according to any one of items 5) to 8) above, further comprising a drum which is rotatable and capable of mounting said plate material thereon, so that the drawing of an image can be performed while moving said plate material by the rotation of said drum.
12) The plate-making apparatus according to item 11) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction parallel to an axis of said drum to perform sub-scanning.
13) The plate-making apparatus according to any one of items 5) to 10) above, further comprising at least one pair of capstan rollers capable of holding and running said plate material to perform sub-scanning.
14) The plate-making apparatus according to item 13) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction orthogonal to the running direction of said plate material to perform main scanning.
15) The plate-making apparatus according to item 11) or 13) above, wherein said ejection head comprises a full line head having almost the same length as the width of said plate material.
16) The plate-making apparatus according to any one of items 5) to 15) above, which comprises a dust-removing member which removes dusts present on the surface of said plate material at least one of before and during the drawing on said plate material.
17) The plate-making apparatus according to any one of items 5) to 16) above, wherein said ink jet drawing device has a stirring member which stirs the oil ink in said ink tank for storing said oil ink.
18) The plate-making apparatus according to any one of items 5) to 17) above, wherein said ink jet drawing device has an ink temperature-controlling member which controls the temperature of said oil ink in said ink tank for storing said oil ink.
19) The plate-making apparatus according to any one of items 5) to 18) above, wherein said ink jet drawing device has an ink concentration-controlling member which controls the concentration of said oil ink.
20) The plate-making apparatus according to any one of items 5) to 19) above, which comprises a cleaning member which cleans said ejection head.
21) A computer-to-cylinder lithographic ink jet printing process comprising:
mounting a plate material onto a plate cylinder;
forming an image directly on said plate material by an ink jet method comprising ejecting an oil ink using the electrostatic field based on signals of image data to manufacture a printing plate; and
performing lithographic printing using said printing plate,
wherein said process uses:
(1) an ink circulation line having the following members a, b and c:
a. an ink jet ejection head,
b. an ink transportation line comprising an ink feed line for feeding said oil ink to said ink jet ejection head and an ink recovery line for recovering said oil ink from said ink jet ejection head, and
c. an ink tank for storing said oil ink;
(2) a cleaning solution feed line for feeding a cleaning solution to said ink transportation line; and
(3) a cleaning solution recovery line for recovering said cleaning solution from said ink transportation line, and
wherein at the time of cleaning, said ink tank is separated from said ink transportation line, said cleaning solution feed line and said cleaning solution recovery line are connected to said ink transportation line, and a cleaning solution is transported to the ink transportation line to perform the cleaning.
22) The computer-to-cylinder lithographic ink jet printing process according to item 21) above, wherein said cleaning solution is circulated at the time of cleaning.
23) The computer-to-cylinder lithographic ink jet printing process according to item 21) or 22) above, wherein the flow rate of said cleaning solution at the time of cleaning is higher than the flow rate of ink at the time of drawing an image.
24) The computer-to-cylinder type lithographic ink jet printing process according to any one of items 21) to 23) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
25) A computer-to-cylinder lithographic printing apparatus comprising:
a plate cylinder for mounting a plate material thereon;
an image-forming unit which forms an image directly on the plate material on said plate cylinder to manufacture a printing plate having formed thereon an image; and
a lithographic printing unit which performs lithographic printing using said printing plate,
wherein said image-forming unit comprises:
an ink jet drawing device having an ink jet ejection head from which an oil ink is ejected using electrostatic field based on signals of image data,
an ink circulation unit comprising:
(1) said ink jet ejection head,
(2) an ink transportation unit comprising an ink feed member which feeds said oil ink to said ink jet ejection head and an ink recovery member which recovers said oil ink from said ink jet ejection head, and
(3) an ink tank for storing said oil ink,
a cleaning solution feed member which feeds a cleaning solution to said ink transportation unit,
a cleaning solution recovery member which recovers said cleaning solution from said ink transportation unit,
a feed side changeover member which separates said ink tank from said ink transportation unit and at the same time, connects said cleaning solution feed member to said ink transportation unit, and
a recovery side changeover member which connects said cleaning solution recovery member to said ink transportation unit.
26) The computer-to-cylinder lithographic printing apparatus according to item 25) above, which comprises a circulation unit which circulates said cleaning solution at the time of cleaning.
27) The computer-to-cylinder lithographic printing apparatus according to item 25) or 26) above, which comprises a flow rate-changing member capable of increasing the flow rate of said cleaning solution at the time of cleaning higher than the flow rate of ink at the time of drawing an image.
28) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 27) above, wherein said oil ink comprises:
a nonaqueous solvent having an electric resistivity of 109 xcexa9cm or more and a dielectric constant of 3.5 or less; and
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
29) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 28) above, wherein said image-forming unit has a fixing device for fixing said ink.
30) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 29) above, wherein said image-forming unit has a plate material surface dust-removing member which removes dusts present on the surface of plate material at least one of before and during the drawing on said plate material.
31) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 30) above, wherein said plate cylinder is rotatable so that the drawing of an image can be performed while moving said plate material by the rotation of said plate cylinder.
32) The computer-to-cylinder lithographic printing apparatus according to item 31) above, wherein said ejection head comprises a single channel head or a multi-channel head and is movable in a direction parallel to an axis of said plate cylinder to perform sub-scanning.
33) The computer-to-cylinder lithographic printing apparatus according to item 31) above, wherein said ejection head comprises a full line head having almost the same length as the width of said plate cylinder.
34) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 33) above, which further comprises an ink-stirring member in said ink tank.
35) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 34) above, which further comprises an ink temperature-controlling member which controls the temperature of the oil ink in said ink tank.
36) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 35) above, which further comprises an ink concentration-controlling member which controls the concentration of said ink.
37) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 36) above, wherein said ink jet drawing device has an ejection head-retreating or approximating member which approximates said ejection head to said plate cylinder at the drawing on said plate material and retreats said ejection head from said plate cylinder except for the drawing on said plate material.
38) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 37) above, wherein said image-forming unit has an ejection head-cleaning member which cleans said ejection head at least at the completion of plate-making.
39) The computer-to-cylinder lithographic printing apparatus according to any one of items 25) to 38) above, wherein said lithographic printing unit has a paper dust-removing member which removes paper dusts generated at the lithographic printing.
As such, in the plate-making apparatus or computer-to-cylinder type lithographic printing apparatus by an ink jet method of ejecting an oil ink using electrostatic field, the ink circulation line is changed over to a cleaning solution at the time of cleaning the ink passage, whereby attachments to the electrode and on the passage of the circulation line can be removed.